Photocell-initiated switching device with dual bimetal switch arms



March 15, 1966 H. -r. ADKINS ETAL PHOTOGELL-INITIATED SWITCHING DEVICE WITH DUAL BIMETAL SWITCH ARMS 2. Sheets-Sheet 1 Filed June 24, 1965 Z 6 2 5 WM: i fi 2 3 LI 4 A :I/l4 n 7 ul M w United States Patent 3,240,907 PHOTOCELL-INITIATED SWITCHING DEVICE WITH DUAL BIMETAL SWITCH ARMS Harold T. Adkins, Marshfield, and Chapin Wallour, Duxbury, Mass., assignors to Sigma Instruments, Inc., a

corporation of Massachusetts Filed June 24, 1963, Ser. No. 290,095 5 Claims. (Cl. 200122) This invention pertains in general to condition-initiated switching devices; and, in particular, to a switching device wherein a set of contacts is thermally operated by a heater element whenever a condition-sensitive element detects a predetermined level of physical condition and wherein manual means may be operated to open or close the set of contacts, the manual means being automatically disabled from exercising its control function whenever a different predetermined level of physical condition occurs.

One object of the present invention is to provide a new and improved switching device for connecting or disconnecting a load and a power source in response to the occurrence of a predetermined level of physical condition.

Another object of the present invention is to provide a condition-initiated switching device including switch contacts which are thermally operated after the detection of a physical condition.

Another object of the present invention is to provide a condition-initiated switching device including switch contacts having magnetic means associated therewith to provide snap-action of said switch contacts.

Another object of the present invention is to provide a condition-initiated switching device including thermally operable switch contacts and a mechanism which may be manually operated to override the condition-initiated operation of the switch contacts, the manually operated mechanism being automatically disabled from exercising its control function whenever there is a change in the level of the physical condition which initiated the automatic control action of the switching device.

Another object of the present invention is to provide a new and improved switching device for connecting or disconnecting a load and a power source in response to the occurrence of a predetermined level of light intensity.

Another object of the present invention is to provide a light-level initiated switching device for controlling the turn on and turn off of luminaries, said switching device including a time delay feature for enhancing the capabilities of the switching device with respect to making the switching device insensitive to short duration changes in light intensity.

Another object of the present invention is to provide a condition-initiated switching device which is relatively simple, reliable, easily constructed and economical.

Although the subject condition-initiated switching device is described, hereinafter, as being particularly applicable for turning on and turning 01f lamps in response to predetermined levels of light intensity, it is to be understood that the condition initiating the controlled switching action may be other than a level of illumination and that the load to be controlled may be other than a lighting load. For example, the condition initiating the control action may be a temperature level, pressure level, humidity level, etc.

Briefly, in accordance with an illustrative embodiment of the present invention, there is provided a switching device having a set of normally-closed bi-metallic contacts. Encompassing one of the bi-metallic contacts is a heating coil which is serially connected with a photo-conductive cell. The ambient light intensity determines the conduc- "ice tivity of the photo-conductive cell; which cell, in turn, controls the amount of current which passes through the heating coil. For example, at sunrise suflicient current is enabled to pass through the heating coil to cause the normally-closed set of bi-metallic contacts to open after a predetermined duration of time, depending on the flexural response of the coil-encompassed bi-metallic contact to the thermal energy imparted thereto. Whenever dusk occurs, the relatively lower conductivity of the photoconductive cell will not permit the passage of sulficient current through the heating coil. As a consequence, after a predetermined duration of time determined by the cooling rate of the coil-encompassed bi-metallic contact, the bi-metallic contacts revert to their normally-closed status. When closed these bi-metallic contacts establish circuit continuity between a power source and a load, or circuit, to be controlled. Of course, it will be understood by those persons skilled in the control arts that the contacts could, if desired, be normally-open instead of normallyclosed so as to connect the power source with the load at sunrise, rather than at dusk.

An important feature of the present invention resides in the employment of a permanent magnet in association with one of the bi-metallic contacts to provide for snapaction of the contacts. For example, when at dusk the coil-encompassed bi-metallic contact which while cooling is slowly moving toward making contact with the other bi-metallic contact, the permanent magnet will, at a certain point in the travel of the coil-encompassed contact, exert sufiicient magnetic attractive force to abruptly pull both of the bi-metallic contacts into normally-closed engagement.

Another important feature of the switching device according to the present invention is the employment of a manually operable cam mechanism for opening or closing the set of contacts and, thus, removing the action of the set of contacts from the influence of the physical condition sensing device; e.g., the photo-conductive cell. The cam mechanism is so arranged with respect to the thermally controlled contact elements that the cam mechanism is automatically disabled from exercising its overriding control function whenever a different predetermined level of physical condition occurs.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

In the drawings:

FIG. 1 is an elevational view showing the conditioninitiated switching device according to the present invention;

FIG. 2 is an elevational view from the left-hand side of the switching device shown at FIG. 1 as viewed along the line 22';

FIG. 3 is a bottom view of the switching device shown at FIG. 1 as viewed along the line 33' shown at FIG. 1;

FIG. 4 is an elevational view of the right-hand side of the switching device in FIG. 1 as viewed along the line 44 shown at FIG. 1;

FIG. 5 is an elevational view showing the back of the switching device of FIG. 1 as viewed along the line 5-5 of FIG. 2;

FIG. 6 is a sectioned elevational view of the conditioninitiated switching device, according to the invention, as viewed along the line 66' shown at FIG. 2;

FIG. 7 is a sectioned view of a portion of the switching device as viewed along the line 7-7 shown in FIG. 5;

FIG. 8 is a schematic diagram showing the electrical connections of the switching device according to the present invention;

FIG. 9 is a view of a sliding cam shown in its uppermost position;

FIG. 10 is a view of a sliding cam shown in its lowermost position; and,

FIG. 11 is an enlarged view of the sliding cam.

As illustrated in FIGS. 1 to 6, the subject conditioninitiated switching device is provided with a mounting frame comprising a front plate and the back plate 21. As shown, the back plate 21 is a generally U-shaped planar member while the front plate 20 is substantially a square-shaped planar member. Both the front plate 20 and the back plate 21 are fashioned from electrical insulating material, such as polyethylene or the like. Insulating spacer members 22, 23 and 24 and their associated screws 25 are provided for rigidly mounting the front and back plates 20 and 21 into a mounting frame (not shown). The insulating spacers 22, 23 and 24 may be fashioned from the same materials as are employed to fashion the front and back plates 20 and 21.

As shown, transducer means such as a photo-conductive cell 26 is mounted on the external face of the front plate 20. Preferably, the cell 26 is a cadmium sulfide cell. As is known when a cadmium sulfide cell is subjected to illumination, its conductivity increases. Any equivalent light responsive device may be used.

Two apertures 27 and 28 are provided in the front plate 20. Also, provided in association with the apertures is a retaining wire member 29 for fastening the photo-conductive cell 26 to the outer surface of the front plate 20. As shown in the drawing, FIGS. 1 and 2, the wire 29 is bent over around the rim 26a of the photoconductive cell 26; the wire 29 when surrounding the cell 26 forming, as shown at FIG. 1, a somewhat elliptical configuration. As shown at FIG. 5, the end portions 29a of the retaining wire 29 protrude through the apertures 27 and 28 and are bent over on the back side of the front plate 20.

As shown at FIGS. 3, 5 and 6, additional apertures 30 and 31 are provided in the front plate 20 so that terminals 26b and 260 of the photo-conductive cell 26 may protrude therethrough.

Two strips or reed elements 32 and 33 are mounted in cantilever fashion, as shown at FIGS. 2, 3, 4, 5 and 6. The reed contact elements 32 and 33 are cantilevered in parallel spaced-apart arrangement. The reed contact elements 32 and 33 are preferably strips of bi-metallic material of identical properties so that changes in the ambient temperature will not affect their relative spacing. As shown at FIGS. 3, 4 and 6, the mounting members 34 and 35, which are secured to the front plate 20 by the screw means 36, serve to support one end of each of the reed contact elements 32 and 33. As shown at FIGS. 5 and 6, the free end of each of the reed contact elements 32 and 33 have the relatively thin tongue portions 32a and 33a fashioned therein.

The reed contact element 32 has affixed near one extremity thereof (the free end thereof) the permanent magnet 36a. Encompassing the reed contact element 33, which is a bi-metallic strip, is a coil 37 of resistance wire, which forms the heating element for thermally actuating the bi-metallic element, causing it to bend laterally when heated.

Shown at FIG. 7 is a cross-sectional detail showing the relative arrangement of the permanent magnet 36a with its reed element 32. As shown, the permanent magnet is fixed to the reed element by the electrically conductive stud element 38, one end of which is enlarged as at 38a to form a good electrical contact surface. Fastened'to the reed contact element 33 by the short stud 39 (one face of which serves as the contact surface) is the magnetizable disc 40. The disc 40 is of a relatively high per meability magnetic material which serves as an armature relative to the permanent magnet 36a.

The heater coil 37 has one of its leads 37a connected to terminal 26b of the photo-conductive cell 26. The other lead 37b of the heater coil 37 is bonded directly to reed 33, as shown in FIG. 6. Also, as illustrated at FIGS. 3, 5, 6 and 8, the electrical lead conductor 41 is electrically bonded with the reed element 33 while the conductor 42 is electrically bonded with the reed element 32.

Also, as illustrated at FIGS. 3, 5, 6 and 8 the conductor 43 is directly connected to the terminal 260 of the photo-conductive cell 26.

Also, as shown at FIGS. 3, 5 and 6, there is provided a manually actuable device such as the cam mechanism illustrated. This manually actuable cam mechanism is comprised of the rocker 44, its firmly connected stud 45 and the sliding cam 46. The rocker 44 is provided with two faces 44a and 44b. Whenever the face 44a is depressed, the rocker 44 will be rotated to a limited degree in a counter-clockwise direction. When the face 44b is depressed, the rocker 44 will be rotated to a limited degree in a clockwise direction. A generally V-shaped spring 47 engaging the central pivot 48 of the rocker bears against two studs 49 and 50 to bias the rocker 44 to the neutral position, as indicated in FIGS. 1, 5 and 6. When in this position it has no influence on the operation of opening of the normally-closed contacts on the read elements 32 and 33. In such a position, only the photo-conductive cell 26, which as hereinafter described with reference to the electrical schematic of FIG. 8, enables energization of the heating element 37 to cause a thermal flexure of the reed element 33 and a separation of the contacts on elements 32 and 33. Two studs 51 and 52 as shown at FIG. 6, mounted on the front and back plates 20 and 21, respectively, are provided for maintaining the upright alignment of the sliding cam element 46. The cam element 46 is preferably provided with an elongated lateral slot 46a engaging the stud 45 of the rocker arm 44. This permits lateral movement of the cam slider 46 with the bi-metallic contact strips 32 and 33 as these strips curve slightly under changing conditions of ambient temperature.

Before describing in detail the effect of actuating the rocker 44, the operation of the electric circuitry will now be described with reference to FIG. 8.

In the schematic shown in FIG. 8, the conductors 41 and 43 are intended to be directly connected at their re spective terminals 60 and 61 across a potential source (not shown). Between the terminals 62 and 61, a load 63 which is to be controlled, is connected. As shown between the terminals 60 and 61 there is a first series circuit comprising the heating coil 37 and the photo-conductive cell 26. The bi-metallic reed element 33 has one of its ends connected to the conductor 41 and is encompassed by the heating coil 37. It is thereby heated to a higher temperature than element 32 whenever current is passed through the coil and will separate from the other reed contact 32 with which it is normally in contact. The conductor 42 is connected with the reed element 32 and the load terminal 62. Assuming that the rocker 44 is in the neutral position, as illustrated in FIGS. 1, 5 and 6, the operation is as follows: whenever sufficient illumination (sunrise) appears the photo-conductive cell 26 exh ibits increased conductivity, thereby enabling a sufficient flow of current from the power source through the heater element 37 between the terminals 60 and 61. As a consequence, the bi-metallic reed 33 will, due to thermal action, flex away from and out of contact with the reed 32 there-- by disconnecting the load 63 from its previous connection with terminal 60 through the conductor 41. Whenever dusk appears the conductivity of the photo-conductive cell 26 will markedly decrease, thereby preventing sufiicient current from passing through the heater coil 37. Shortly thereafter, the reed element 33 will resume its normal position; i.e., make contact with the reed 32 thereby energizing the load 63 again.

As may be appreciated from the foregoing discussion with the rocker 44 in the neutral position indicated in FIGS. 1, 5 and 6, the connection or disconnection between the reeds 32 and 33 is solely under the influence of the photo-conductive cell 26. However, the influence of the cell 26 may be overridden by manually actuating the rocker 44. If, for example, during daylight hours the reeds 32 and 33 are not in contact due to the action of the heating coil 37, face 44a of the rocker 44 may be depressed to rotate the rocker in a limited counter-clockwise direction. The sliding cam 46 will, as shown in FIG. 9, move upward; and, as a result, the tongue portions 32:: and 33a of the reeds 32 and 33, will enter the slot 73 of the cam 46. As the cam moves downwardly, the nose portions 71 and 72 of the cam 46 force the open reeds 32 and 33 into contact. The width of the slot 73, as may be appreciated from FIG. 11, is relatively narrow so that the reeds 32 and 33 remain in contact, thereby causing energization of the load 63. Due to the lower shoulder portions of the noses 71 and 72, the tongue portions 32a and 33a cannot, without further manual actuation, of the rocker 44 become released from the slot 73. As a consequence, when as is illustrated at FIG. 9, the cam 46 slides upwardly, the reeds 32 and 33 remain in their closed condition.

If during hours of darkness the reeds 32 and 33 are in their closed condition thereby energizing the load 63, this condition may be overridden by depressing the face 44/) of the rocker 44 whereby the sliding cam 46 will be moved downwardly, as shown at FIG. 10. As a result, the tongue portions 32a and 33a will, by virtue of the downwardly moving nose portions 74 and 75, come to rest in the slots 76 and 77. In this position the separation between the reeds 32 and 33 is such as to maintain the reeds in their separated or opened condition, thereby deenergizing the load 63. However, when the tongues 32a and 33a are in the position shown at FIG. 10, and daylight reappears thereby increasing the conductance of the photo cell 26, the heater element 37 is again energized thereby thermally moving the reed 33 away from the reed 32. As a result, the tongues 32a and 33a move toward the left and right, respectively (according to the orientation shown at FIGS. and 11), whereby the spring element 47 causes the rocker 44 to rotate in a counter-clockwise direction and thereby assume its neutral position, as shown at FIGS. 1, 5 and 6.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

ll. A switching device for controlling the flow of electric power from a power source to a load, comprising: a housing, a pair of contact strip elements on said housing connected in series with the source and the load, at least one of said contact elements being of bi-metallic material; a heating coil on said housing, operatively associated with said bi-metallic contact element; transducer means on said housing connected in series with said heating coil, said series connected heating coil and transducer means being connected across said power source; and, manually operable means on said housing for opening and closing said contact strip elements, said manually operable means including a slider having a narrow slot therethrough and two spaced-apart slots therethrough, said contacts being maintained in a closed condition when in said narrow slot and being maintained in said separated condition when in said respective spaced-apart slots,

2. A switching device for controlling the flow of electric power from a power source to a load, comprising: a housing, a pair of contact strip elements on said housing connected in series with the source and the load, at least one of said contact elements being of bi-metallic material; a heating coil on said housing operatively associated with said bi-metallic contact element; transducer means on said housing connected in series with said heating coil, said series connected heating coil and transducer means being connected across said power source; and, manually operable means on said housing for opening and closing said contact strip elements, said manually operable means including a slider having a narrow slot therethrough and two spaced-apart slots therethrough, said contacts being maintained in a closed condition when in said narrow slot and being maintained in said separated condition when in said respective spaced-apart slots, said contacts being maintained in said separated condition by said spaced-apart slots operate in response to said condition responsive actuation of said heat transferring means to move said slider whereby said contacts resume a closed condition.

3. In combination with a switching device including a housing, a pair of contacts mounted on said housing which are operated by a heating element in response to the occurrence of a predetermined physical condition, manually operable means for opening or closing the contacts on said housing; said manually operable means comprising a movable member having two spaced-apart slot portions therethrough, a wide slot portion contiguous with said spaced-apart slot portions, and a narrow slot portion contiguous with said wide slot portion, the selective movement of said movable member enabling said pair of contacts to become selectively situated in said narrow slot, said wide slot or said spaced-apart slots, respectively; said contacts being maintained in contact when in said narrow slot, said contacts being operated solely by said heating element when in said wide slot, said respective contacts being maintained separated when in said respective spacedapart slots.

4. The combination, according to claim 3, wherein said manually operable means includes a spring biased rocker arm for moving said movable member, said movable member including nose portions intermediate said spacedapart slots and said wide slot, said nose portions maintaining said contacts separated in said respective spacedapart slots when said movable member is so selectively moved; said heating element being responsive upon change of heating conditions to actuate said contacts to move whereby said spring biased rocker arm moves the movable element so that said contacts move into said wide slot.

5. The combination, according to claim 4, wherein both said contacts are strips of bi-metallic material having identical properties, said movable member including an additional elongated lateral slot therethrough, said rocker arm having a stud thereon protruding into said lateral slot, said movable member being enabled to slide laterally along said stud as said bi-metallic strips curve due to changing ambient temperature conditions.

References Cited by the Examiner UNITED STATES PATENTS 2,303,153 11/1942 Woodworth 200122 2,571,654 10/1951 Beard et al. 200122 2,762,885 9/1956 Foster 200-139 2,900,520 8/1959 Frank 250-206 3,056,035 9/1962 Bernheim 250239 X BERNARD A. GILHEANY, Primary Examiner. 

1. A SWITCHING DEVICE FOR CONTROLLING THE FLOW OF ELECTRIC POWER FROM A POWER SOURCE TO A LOAD, COMPRISING: A HOUSING, A PAIR OF CONTACT STRIP ELEMENTS ON SAID HOUSING CONNECTED IN SERIES WITH THE SOURCE AND THE LOAD, AT LEAST ONE OF SAID CONTACT ELEMENTS BEING OF BI-METALLIC MATERIAL; A HEATING COIL ON SAID HOUSING, OPERATIVELY ASSOCIATED WITH SAID BI-METALLIC CONTACT ELEMENT; AND, MANUALLY ON SAID HOUSING CONNECTED IN SERIES WITH SAID HEATING COIL, SAID SERIES CONNECTED HEATING COIL AND AND TRANSDUCER MEANS BEING CONNECTED ACROSS AND POWER SOURCE; AND, MANUALLY OPERABLE MEANS ON SAID HOUSING FOR OPENING AND CLOSING SAID CONTACT STRIP ELEMENTS, SAID MANUALLY OPERABLE MEANS INCLUDING A SLIDER HAVING A NARROW SLOT THERETHROUGH AND TWO SPACED-APART SLOTS THERETHROUGH, SAID CONTACTS BEING MAINTAINED IN A CLOSED CONDITION WHEN IN SAID NARROW SLOT AND BEING MAINTAINED IN SAID SEPARATED CONDITION WHEN IN SAID RESPECTIVE SPACED-APART SLOTS. 